Some types of IMDs provide therapeutic electrical stimulation to tissue of a patient via electrodes of one or more implantable leads. Examples of such IMDs include implantable cardiac pacemakers, cardioverter-defibrillators, or the like. An IMD may deliver electrical stimulation to the tissue via electrodes of implantable leads in the form of pacing stimulation, cardioversion stimulation, defibrillation stimulation, or cardiac resynchronization stimulation. In some cases, electrodes carried by the implantable leads may be used to sense one or more physiological signals to monitor the condition of a patient and/or to control delivery of therapeutic electrical stimulation based on the sensed signals.
An IMD may be exposed to an external energy field for any of a number of reasons. For example, one or more medical procedures may need to be performed on the patient within whom the IMD is implanted for purposes of diagnostics or therapy. In particular, the patient may be examined using a disruptive energy field produced, for example, by a magnetic resonance imaging (MRI) scan, computed tomography (CT) scan, or other medical procedure that produces a magnetic field, electromagnetic field, electric field or other disruptive energy field. The field may be disruptive in the sense that it may disrupt operation of the IMD in some manner.
In some examples, operation of the IMD, such as delivery of electrical stimulation by the IMD, may be impacted by a medical procedure, such as an MRI scan or CT scan. For example, a disruptive energy field may impact the ability of the IMD to deliver therapy. Also, delivery of wireless telemetry may impact the medical procedure. For example, wireless telemetry may induce noise in an MRI scan. For these reasons, it may be desirable to disable operation of the IMD during a medical procedure.